Why would my MSG instruction remain at enable without an error or a time out?

I have a new HI 1756-2WS module.  When I do a MSG instruction to run a command, it will lock up indicating it is enabled, but it never goes to done or error.  Why would the MSG instruction remain at enable without an error or a time out? 

Sometimes it seems that the MSG instruction would work for channel 1, but not for channel 0.

The issue with the MSG instructions getting "stuck" is not a new one and this issue has come up before when someone copied the code from one program into another program that was created in a later version of RS Logix 5000.  You should delete the instruction and enter it in manually to correct the problem.  

Another possible issue is that they run so fast in the ControlLogix system, that they can run multiple times without you knowing it.  Placing a one shot in front of the MSG instruction will prevent this from happening.

If the instruction fails it is a code/communications problem, not an instruction problem.  If one MSG instruction works properly, then the module is working and communication is good.  So if the MSG instruction fails, it would be a problem with that instruction.  If it was a problem with the module, the command may fail, but the MSG instruction would complete.

If you have a condition where you can send a command to one channel, but not the other, then the module may have a corruption in the memory.  Set the channel back to default parameters and start over again.  This would normally clear any corruption and allow things to work properly again.